The purpose of this study was to determine the relation between caries experience, water fluoride level and socioeconomic class among the 15-year-old school children of Tamilnadu. The study children were stratified on the basis of water fluoride level and socioeconomic (SE) class. The children were divided into low, medium and high SE classes. There was a highly significant (P<.OOI) difference in the carious experience of 15-year-old children from low fluoride (LF) areas in relation to the SE class. The low SE class having the highest caries experience. There was almost no difference between the caries experience of low SE class 15-year-old children from the LF area and high fluoride (HF') area (Z<1.96 and P>O.O5). The difference between caries experience of 15-year-old children from LF and HF areas was not statistically significant (Z<1.96 and P'>0.05). The present study has indicated towards the need of provision, of more vigorous preventive efforts in lower SE class children in both the urban and rural population.